Belt tension and tracking adjustment device for portable belt sanders



P. LUBAS BELT TENSION AND TRACKING ADJUSTMENT DEVICE FOR PORTABLE BELTSANDERS Filed May 11, 1960 A ril 17, 1962 2 Sheets-Sheet 1 INVENTORJoseph P Lubas WITNESS April 17, 1962 J. P. LUBAS 3,029,563

BELT TENSION AND TRACKING ADJUSTMENT DEVICE FOR PORTABLE BELT SANDERS 2Sheets-Sheet 2 Filed May 11, 1960 mm hm P um v51? f :E WU

INVENTOR. Joseph P Lubas ORNEY WITNESS United States Patent OfiicePatented Apr. 17, 1962 3,029,568 BELT TENSION AND TRAQKHNG ADJUSTMENTDEVICE FOR P DRTAELE BELT SANDERS Joseph P. Lnbas, Linden, NJ, assignorto Diehl Manufacturing Company, onieryiile, Ni, a corporation of NewJersey Filed May 11, 1960, st. No. 23,377 1 Claim. (Cl. 51-470) Thisinvention relates to portable, power-operated, belt sanding machines. Itis customarily in machines of this type to have an endless abrasive belttrained over two pulleys. The belt-driving pulley is journalled in themachine frame at the rear end while the idler pulley is journalled atthe forward end. A pressure pad is located between the pulleys toprovide a fiat platen to maintain the lower run of the belt against theWork being sanded. Due to the requirement of loading and unloading theabrasive belts and also due to the manufacturing variations in the beltstructure itself it is necessary to provide mounting structure for theidler pulley whereby it may be shifted into and out of parallelism withrespect to the driving pulley and adjusted to provide proper tension andtracking of the belt.

This invention relates more particularly to structure for adjusting thetension and tracking of the abrasive belt of a belt sanding machine andhas as an object an arrangement for supporting the idler pulley wherebysaid adjustments can be made with dispatch and convenience employingsimple, readily-assembled structural elements.

With the above and other objects in view, as will hereinafter appear,the invention comprises the devices, combinations and arrangements ofparts hereinafter set forth and illustrated in the accompanying drawingsof a preferred embodiment of the invention, from which the severalfeatures of the invention and the advantages attained thereby will bereadily understood by those skilled in the art.

FIG. 1 is a side elevational view of a sanding machine embodying theinvention.

FIG. 2 is a longitudinal sectional view, partly in plan, taken on line2-2 of FIG. 1.

FIG. 3 is a detail perspective view of an essential element of thedevice of FIG. 1.

Referring to FIG. 1, there is shown a sanding machine comprising anintegral frame having a side wall it a top wall 11 and a bottom wall 12.Formed integrally with the top wall 11 is a motor housing 13 having acover plate 14. A handle 15 is secured to the motor housing 13 and to anend wall portion 16 of the frame.

A driving pulley 17 is journalled in the frame at the rear end'and anidler pulley 18, located at the forward end, is supported by structuresabout to be described. An endless abrasive belt 19 is trained over thepulleys as shown.

The bottom wall 12 has secured thereto a resilient pad 20, preferablymade of cork, and a polished sheet steel ply 21 to form a smooth platenfor holding the bottom run of the belt 19 against the work to be sanded.

Referring now to FIG. 2, the pulley 18 is journalled on a pin 22 securedto one end of a gooseneck bracket 23 made preferably of aluminum. A stemportion 24- of the bracket 23, extending essentially at right angles tothe axis of the pin 22, carries a transverse pin 25 and is formed at itsfree end with a step portion 26.

A wear plate 27, made preferably of sheet steel, is bent to conform tothe step portion 26 and is secured to the stem portion 24.by means of adrive pin 28. One

end of the wear plate 27 is bent away from the stem portion 24 and isformed with an aperture 29 for receiving one end of a tension spring 30,the other end .2 being anchored by a pin '31 secured in ribs 42 formedon the side wall 10 as shown.

The stem portion 24 of the bracket 23 slides within a channel-shapedsheet metal cam 32 (shown in FIG. 3) which is secured by screws 33 tospaced bosses 34 and 35 formed on the side wall 10. The bracket 23 isguided in its endwise movement by the pin 25 which engages slots 36formed in the opposed side walls of the cam 32.

An adjusting screw 37, threaded into a boss 38 formed on the side wall143 has a terminal portion 39 which bears against the wear plate 27 asshown. A bias spring 4i) retains the screw 37 against rotation.

It will be seen that the single spring 36 applies bothforwardly-directed endwise and side-wall directed lateral forces to thebracket 23. Looking for removal of the abrasive belt 19 isaccomplished'by pushing in on the idler pulley 18 to retractitrearwardly until the for- I ward edge 41 of the wear plate 27 falls overthe terminal portion 39 of the adjusting screw 37, as shown in thedotted lines of FIG. 2. This inclined locked posi tion of the pulley 18facilitates removal of the old belt and installation of a new one.

A cover piece as secured to the top wall 11 and bottorn wall 12, bymeans of screws id-serves as a stop for engagement with abutmentportionjs of the bracket 23 to limit the maximum forward movement of thebracket 23.

To release the idler pulley 2.8 after a new belt has been installed, aside pressure is applied tothe pulley 1% which causes the bracket 23 topivot about the pin 25 riding in the slots 36. This allows the forwardedge 41 of the wear plate 27 to clear the terminal portion 39 of thescrew 37, whereupon the spring 30 pulls the bracket forward to establishand maintain tension on the belt 19.

Adjustment of the screw 37 provides the proper positioning of the axisof the pulley 18 to secure proper tracking of the belt 19.

Having thus set forth the nature of my invention, what 1 claim hereinis:

In a portable, power-operated sanding machine having an endless abrasivebelt, a frame formed with a vertical side wall, a rearwardly positionedpulley for driving said belt, a forwardly positioned idler pulley forguiding said belt, means supporting said idler pulley coma prisingvertically spaced-apart bosses formed on said side wall between saidpulleys, a channel-shaped cam positioned horizontally between saidbosses and secured thereto, parallel slots formed in the horizontalopposing walls of said cam, a gooseneck bracket having a stem portionslidable within said cam, means secured to said bracket journalling theidler pulley thereon, pin means secured to said stem portion inengagement with said slots for guiding said bracket, the free end of thestem portion being formed with a step portion defining a forward edge, awear plate secured to the stem portion and covering the step portion andthe forward edge, single tension spring means secured at one end to saidwear plate and at the other end to said side wall for applyingforwardly-directed endwise and side-wall directed forces to saidbracket, and manually adjustable means secured to said side wallrearwardly of said tension spring to limit the lateral movement of saidstep portion toward the side wall and to retain the bracket in arearwardly retracted position for belt removal.

References Cited in the file of this patent UNITED STATES PATENTS

